Update Ruby version to 3.1 in GitHub Actions workflow

Author: mehyaa

.github/workflows/docs.yml

@@ -45,7 +45,7 @@ jobs:
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "3.4"
+          ruby-version: "3.1"
           bundler-cache: true
           working-directory: ./docs